Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['f', 'a', '521', '5489', '1917', 'i', 'u', 'g', 'D', 'l']

6, 1, 521, 5489, 1917, 9, 21, 7, 4, 12